Pre-stressed concrete foundation for a marine building structure

ABSTRACT

A pre-stressed marine foundation includes a concrete base to be placed on a sea bed, a body placed over the concrete base, and a concrete platform. The body includes closed sections, each closed section composed of a pre-stressed concrete segmented column that has an upper extreme and a lower extreme joined at the base, and opened sections joined at sides of the closed sections, each open section composed of a structured beam frame. The concrete platform is joined at the upper extremes of the concrete columns.

PRIORITY STATEMENT

The present application claims the benefit under 35 U.S.C. §119(e) ofU.S. Provisional Patent Application Ser. No. 61/352,296 to theinventors, filed Jun. 7, 2010 and entitled “PRE-STRESSED CONCRETEFOUNDATION FOR A MARINE BUILDING STRUCTURE”, the entire contents ofwhich is hereby incorporated by reference herein.

BACKGROUND

1. Field

The example embodiments in general relate to the foundation for a marinebuilding structure, and more specifically to a pre-stressed foundationto support off-shore marine structures such as wind power generators.

A portion of the disclosure of this provisional patent applicationdocument contains material which is subject to copyright protection. Thecopyright owner has no objection to the facsimile reproduction by anyoneof the patent document or the patent disclosure, as it appears in thePatent and Trademark Office file or records, but otherwise reserves allcopyrights associated with this document.

2. Related Art

Certain prior art teaches diverse marine foundations, for example, U.S.Pat. No. 4,304,506 which describes a marine structure that has a baseand foundation means projecting itself deep in the base to set itself ina deep marine bed, the foundation comprising a system of walls withmeans to hold it in both sides of the wall.

U.S. Patent Application Publication No. US-2009/0191004 describes adesign method and construction of a cubic formed marine foundationstructure. The method includes a first stage having a design phase and asecond stage having an installation phase. In the first stage, designparameters are given relative to the weights set on the foundationstructure, the profile of the grounds over its installation location,allowable tolerances in installation, certain parameters utilized tocalculate the minimum diameter and longitude of the cube's borders. Thesize of the cube is utilized to simulate load situations and penetrationin the foundation terrain. The foundation, as the majority of thefoundations of the prior art, relates to marine currents and thereforeare designed to resist these currents.

SUMMARY

An example embodiment is directed to a pre-stressed marine foundation.The foundation includes a concrete base to be placed on a sea bed, and abody placed over the concrete base. The body includes a plurality ofclosed sections, each closed section composed of a pre-stressed concretesegmented column, each column having an upper extreme and a lowerextreme joined at the base, and a plurality of opened sections joined atsides of the closed sections, each open section composed of a structuredbeam frame. A concrete platform is joined at the upper extremes of theconcrete columns.

Another example embodiment is directed to a pre-stressed marinefoundation comprising a concrete base, a body placed on the concretebase, the body having a triangular cross-section formed by threeequally-spaced segmented pre-stressed vertical concrete columns withthree beam frames joined in an open space between the three spacedsegmented vertical concrete columns, and a concrete platform joined toupper ends of the vertical concrete columns.

Another example embodiment is directed to a pre-stressed marinefoundation comprising a base having a sloped side surface, a towerplaced on the base, the tower having a triangular cross-section formedby a plurality of spaced segmented pre-stressed vertical concretecolumns with a plurality of reinforcing beam frames joined in openspaces between the spaced segmented vertical concrete columns to realizea tower with annular structure and said triangular cross-section, and aplatform joined to upper ends of the vertical concrete columns.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments will become more fully understood from the detaileddescription given herein below and the accompanying drawings, whereinlike elements are represented by like reference numerals, which aregiven by way of illustration only and thus do not limit the exampleembodiments.

FIG. 1 shows a perspective view of the pre-stressed concrete marinefoundation in accordance with an example embodiment.

FIG. 2 shows an elevated lateral view of the pre-stressed concretemarine foundation in accordance with an example embodiment.

FIG. 3 shows an upper view of the pre-stressed concrete marinefoundation in accordance with an example embodiment.

FIG. 4 shows a lower view of the foundation according to an exampleembodiment.

FIG. 5 shows a view of a concrete segment according to an exampleembodiment.

FIG. 6 shows a view of the joint of the column with the beam frameaccording to an example embodiment.

DETAILED DESCRIPTION

As to be shown and described in more detail hereafter, the pre-stressed(post-tensioned) concrete marine foundation of the example embodiments,due to its structural design and combination of materials of which it ismade, is designed so as to provide a stronger resistance, durability andsupport than concrete and steel marine foundations of the prior art.

As to be shown and described in more detail hereafter, the exampleembodiments are directed to a ring-shaped or annular pre-stressedconcrete marine foundation structure that is designed to resist marinecurrents, and which may offer a stronger resistance, settling, supportto mount and/or place or mount different structural elements thereon.

The following parts list is provided to aid the reader and should beoccasionally referred to for convenience of understanding.

PARTS LIST

-   -   10 pre-stressed marine concrete foundation;    -   11 concrete base;    -   D1 greater diameter of the base;    -   D2 lesser diameter of the base;    -   116 base sloped surface;    -   117 aperture in the base;    -   118 step in the base;    -   12 body;    -   13 closed sections;    -   13 a, 13 b and 13 c pre-stressed concrete columns;    -   130 concrete segment;    -   14 opened sections;    -   14 a, 14 b and 14 c beam frames;    -   15 platform;    -   132 external face;    -   133 internal face;    -   134 a and 134 b lateral faces;    -   135 upper side;    -   136 lower side;    -   137 vertical ducts;    -   138 horizontal ducts; and    -   140 beams.

FIG. 1 shows a perspective view of the pre-stressed concrete marinefoundation in accordance with an example embodiment; and FIG. 2 shows anelevated lateral view of the pre-stressed concrete marine foundation inaccordance with an example embodiment. The pre-stressed concrete marinefoundation 10 is a ring-shaped reinforced and post-tensioned concretestructure in combination with a framework of beams (See FIG. 1, openedsections 14, for example). The pre-stressed concrete marine foundation10 is designed to support loads to which it is subject, such as theweight of the load, the movement of the waves and/or seismic events. Theexample embodiments thus are designed to overcome all of the drawbacksof prior art previously discussed.

As illustrated in FIGS. 1 and 2, the base 11 comprises a body offrusto-conical shape, having a determined thickness. Base 11 has adiameter D1 that is reduced gradually to a diameter D2 from which risesa body 12 of the foundation 10. Diameter D1 at the bottom of the base 11is greater that the diameter of the body 12, whilst diameter D2 at thetop of base 11 where it meets body 12 and the diameter of the body 12are substantially the same. The amplitude of the base 11 providesstability to foundation 10 against frontal loads resulting from wavesand marine currents. The shaped section of the base 11 provides asurface 116 that has a slope.

The surface 116 serves two purposes. Referring to FIG. 2, on the onehand, the angled slope of surface 116 has a purpose of deflecting watercurrents that it faces upward, thus reducing the risk of horizontaldisplacement of the foundation 10. In addition, surface 116 is pressedby the weight of the water over it. This weight assists in maintainingthe base 11 on the marine bed, and counteracts the inertial moment thatis caused by the superficial marine currents that might tend to overturnthe foundation 10.

FIG. 3 shows an upper view of the pre-stressed concrete marinefoundation in accordance with an example embodiment. Referring to bothFIGS. 2 and 3, the surface of diameter D2 of base 11 includes a step 118that serves as a guide for the placement of the columns and frames ofbody 12. In addition, the base 11 incorporates the necessary means toallow pre-stressing of concrete columns (closed sections 13) of body 12with base 11, such that the base 11 and the closed sections 13 work as amonolithic structure.

Foundation 10 includes the base 11, the body 12 and a platform 15 thatare built and assembled in a wharf or at the coast and is takenassembled to the site where the construction will be set. There aredifferent techniques for the transportation of constructions overfloating structures. At the construction site, the marine bed is cleanedand leveled; thereafter the foundation 10 is sunk and set. The levelingof the terrain can be carried out by known methods in this matter, forexample, with rocks. In other embodiments, the marine foundation may beequipped with a net of horizontal and vertical pipes, interconnected andembedded within the concrete base 11, including nozzles in their endsfor injecting a pressurized water jet to remove the sand under thefooting and clean the marine bed. Such pressurized water jet is producedwhilst the marine foundation 10 is being sunk.

FIG. 4 shows a lower view of the foundation 10. As best shown in FIG. 4,base 11 has an aperture 117. Aperture 117 facilitates the sinking of thefoundation 10. In addition, the aperture permits the anchoring of thefoundation 10 on the marine bed. Once the foundation 10 has been placed,concrete is strained over the base 11 and the aperture 117 to form aconcrete layer thus providing an additional weight to the foundation 10to ensure it does not move.

A tower of the example embodiment is composed of a body 12, whosepurpose is to support the platform 15 that is placed above sea level.

As illustrated best in FIGS. 2 and 3, body 12 is formed by three closedsections 13. Each closed section includes alternated reinforced andpre-stressed concrete columns (13 a, 13 b and 13 c); with three opensections 14, each open section comprising beam frames (14 a, 14 b and 14c) that in combination form an annular structure. This annular structurethus forms the body 12 which is hollow in its center.

Body 12 as illustrated in the figures, has a transversal triangularsection (See FIG. 3, for example). Notwithstanding, any geometry couldbe used; for example, the body 12 could include more than three columnsforming a polygonal body. In addition, in the center of the body 12other columns could be incorporated. However, the triangularconfiguration appears to offer the desired resistance against thelateral loads produced by the waves and marine currents. In addition, abody 12 formed of three columns offers a broader surface above base 11for the circulation of water between the columns.

The polygonal geometric configurations of body 12 that have a largernumber of columns may provide a better resistance to the flow of marinecurrents. However, such a construction may result in a less efficientperformance and its construction could be more expensive.

Body 12 of the foundation 10 incorporates three pre-stressed concretecolumns (13 a, 13 b and 13 c) spaced in between, that extend length andwidth wise on the marine pre-stressed concrete foundation 10 on theapexes of the triangular transversal section of body 12 joined laterallyto the beam frames (14 a, 14 b and 14 c).

FIG. 5 shows a view of a concrete segment according to an exampleembodiment. Each pre-stressed concrete column (13 a, 13 b and 13 c) isformed by concrete segments 130 that have a semicircular shape. Asegment of concrete 130 is shown in FIG. 5, and according to the exampleembodiments, have the same dimension and shape, so that each segment 130can be fabricated in standardized formworks.

Segments 130 have the shape of a cylindrical segment that has an arch ofapproximately 110°. Each concrete segment 130 has an external face 132and an internal face 133 with two lateral faces 134 a and 134 b of agiven thickness. These segments also have an upper side 135 and a lowerside 136. Within segments 130 there are a plurality of vertical ducts137 and optionally, horizontal ducts 138 to introduce and secure withinthe same vertical and horizontal pre-stressing tendons, to join segments130 that are piled vertically. Through each of these vertical ducts 137are introduced pre-stressing tendons and through the pre-stressingtendons the concrete segments 130 remain fixed and firmly joined,forming in this manner each concrete column 13 a, 13 b and 13 c whosestructural properties are similar to one corresponding to a monolithicstructure. The pre-stressing vertical tendons are introduced and securedby means and methods well known to those persons skilled in the art.

The pre-stressed concrete semicircular segments 130 are piledvertically, one on top of the other, edge to edge, to form the body 12of the foundation 10, in accordance with the embodiment illustrated inFIGS. 1 and 2, each concrete column 13 a, 13 b and 13 c comprising foursegments 130. The segments 130 are built at the sea coast or atworkshops near to the docks and taken to the off-shore constructionsite. However, one with ordinary skills in the pertinent art wouldrealize that each column can be built from more or less than fourconcrete segments 130, the selection of which depends on the design andsize of the foundation 10 and construction as well as transportconsiderations.

As would be evident from the present disclosure to one with ordinaryskill in the art, the concrete columns 13 a, 13 b and 13 c may also bemanufactured in any geometry and not only in the shape of semicirculartransversal section columns. For example, the columns 13 a, 13 b and 13c can have a circular, polygonal or triangular transversal section,including one in another shape such as one incorporation various lobes.In addition, columns 13 a, 13 b and 13 c could be straight or could beshaped such that the upper segments 130 would have a lesser diameterthan the lower segments 130 it forms, or could be a “bottle neck” typewherein and for example two lower segments 130 have a greater diameterthan the two upper segments 130 in a same column.

FIG. 6 shows a view of the joint of the column with the beam frameaccording to an example embodiment. According to the exampleembodiments, the pre-stressed semicircular concrete columns (closedsections 13) are joined laterally to the beam frames (open sections 14)by means of a union that allows the columns and frames to workstructurally as one unit.

As shown best in FIG. 5, the body 12 of the pre-stressed marinefoundation 10 is preferably composed of three beam frames (14 a, 14 band 14 c) forming three sections termed jointly open sections 14. Asshown in FIG. 6, each of these frames comprises a plurality ofstructured beams 140.

The beams 140 can be manufactured in steel or in concrete. Concretebeams have a better result when faced with the corrosion of sea water,while steel beams have an elasticity module that renders a betterperformance when faced with the efforts of traction and compression ofwater current and at the inertial moment generated by the structure whenplaced over the foundation, for example, an eolic generator that isexposed to the wind strain. In both cases, beams 140 can bepre-assembled sections, such as beam panels that are connected to theconcrete segments as these are being placed.

In the event of a steel metallic frame, it is assembled by weldingand/or bolts and/or screws with or without reinforcement elements. Asshown in FIG. 6, in one example, it is joined by means of a welding ofthe metallic beams 140 to the reinforcement rods of concrete segments130 of columns 13 a, 13 b and 13 c, such that each of the segments 130is joined to the beam frames 14 a, 14 b and 14 c. In this example, ametallic beam 140 is welded to metal inserts embedded within theconcrete segment 130. The metal inserts can be placed to provide ajoint, either to the beam 140 and as well to join (through a ‘seam”)with vertical pre-stressing strands in the segment 130. The metallicbeam 140 may be protected internally by injection of pressurized mortarand externally by applying an epoxy coating, for example. The beams 140can be structured of any well known manner to form a determinedarrangement, for example, as a honeycomb structure or an included beamstructure, while each element is joined to an upper module and/or alower adjacent module.

In the event that concrete beams 140 are used, the beams 140 may alsoinclude internal ducts, to allow the introduction of horizontal ordiagonal pre-stressing tendons, such that a same horizontal or diagonalpre-stressing tendon may hold the concrete segments 130 as well as thebeams 140.

The beam frames 14 a, 14 b, 14 c have as purpose the structural supportof the pre-stressed marine foundation 10 and of joining the pre-stressedsemicircular cement segments 130 while it permits the flow of waterthrough it.

The concrete base 11, and the body 12, comprising concrete segments 130and beams 140, are assembled on a sea barge in the dock, transported tothe erection site, and finally sunk in at the erection site. Once thebody 12 of the marine foundation structure is placed and post-tensionedin site, it is placed over the same one concrete platform 15, preferablyof a circular form, that serves as a base for other structures, forexample, a petroleum platform or an eolic generator, or for example, apre-stressed concrete tower for a wind power generator.

The ends of body 12 are raised above the sea level, such that theprincipal portion of body 12 is submerged in water, while only theextremes arise from the sea at a proper height above the levels oftides.

As shown in the figures, platform 15 comprises an upper circularconcrete base that has a determined thickness. As shown in the figures,the diameter of platform 15 is greater than the diameter of body 12, andmay include accessories and protrusions necessary to support aninstallation. If the installation is a concrete tower for eolicgenerators, this includes means to anchor the tower to the foundation.The platform 15 has proven efficient with the triangular configurationof body 12; otherwise it could prove to be overly heavy.

Additionally, the lower face could include means such as a step orgrooves so that the platform 15 may adapt to body 12 of the foundation10. The platform 15 can also include ducts to introduce pre-stressingcables such that base 11, body 12 and platform 15 are joined by means ofpre-stressing cables and the entire structure functions as a monolithicstructure.

In accordance with the example embodiments, the pre-stressed concretefoundation 10 is capable of supporting large forces in a lateraldirection without collapsing, without inclining and without significantstructural damages. Also, corrosion has a lesser effect on the concretestructure.

Since the pre-stressed marine concrete foundation 10 is designed tooperate in areas subject to seismic activity, the advantage and benefitshall be that of enduring principally two types of environmental forces.These are: the forces due to waves and the forces imposed over the base11 due to earthquakes.

In regard to those forces derived from waves, the referenced design tothe body of the pre-stressed marine concrete foundation, particularly tothe straight metallic beam frames (14 a, 14 b and 14 c) upon existing aspace between the beams 140 that form spaces without impacting directlyon the pre-stressed marine concrete foundation 10, results in astructure not being weakened by the forces derived from waves andthereby the life span of the pre-stressed marine concrete foundation 10shall extend beyond those of prior art foundations.

The marine foundation 10 may have an example height between 10 to 30meters from the sea bed. The definitive location of the foundations arestudied and prepared to receive the foundation with severalpossibilities:

ROCK BED COVERED BY A THIN LAYER OF SAND. The foundation will be loweredto the sand bed level and a water pump from the barge will injectpressurized water through the pipe system to disperse the sand and lowerthe foundation to the rock bed. At this time, stone wedges are used tolevel the foundation (plumb). A trompe is lowered to the center bottomof the base 11 and concrete is pumped to fill all the aperture 117 (seeFIG. 4) of the base 11. The amount of concrete can be as much as neededto use it as a bottom weight necessary to stand the forces created bythe tower and/or other causes.

IRREGULAR SOIL. Such types of soils need stone to support the foundation10. The process stands lowering the foundation 10 in the marine bed andcasting concrete in the aperture 117 of the base, as mentioned before.The concrete base 11 can be prepared with perforations to drill throughmicro piles anchored in deeper rock beds.

The example embodiments being thus described, it will be obvious thatthe same may be varied in many ways. For example, the body 12 of thefoundation 10 could include concrete blocks placed between the concretecolumns. Additionally, the platform 15 could be built in steel and itnot be held by pre-stressing to body 12 of the foundation 10. Suchvariations are not to be regarded as departure from the exampleembodiments, and all such modifications as would be obvious to oneskilled in the art are intended to be included within the followingclaims.

1. A pre-stressed marine foundation, comprising: a concrete base to beplaced on a sea bed, a body placed over the concrete base, the bodyincluding: a plurality of closed sections, each closed section composedof a pre-stressed concrete segmented column, each column having an upperextreme and a lower extreme joined at the base, and a plurality ofopened sections joined at sides of the closed sections, each opensection composed of a structured beam frame, and a concrete platformjoined at the upper extremes of the concrete columns.
 2. The foundationof claim 1, wherein the body has a triangular cross-section formed bythree segmented pre-stressed concrete columns and three beam framestherebetween.
 3. The foundation of claim 1, wherein each beam frameincludes a plurality of beams selected from concrete beams or metallicbeams.
 4. The foundation of claim 1, wherein concrete segments formingeach of the concrete columns are semicircular and have substantially thesame form and same dimensions.
 5. The foundation of claim 1, wherein thebase includes an aperture.
 6. The foundation of claim 1, furthercomprising a concrete layer added to the base to increase weight of thebase.
 7. A pre-stressed marine foundation, comprising: a concrete base,a body placed on the concrete base, the body having a triangularcross-section formed by three equally-spaced segmented pre-stressedvertical concrete columns with three beam frames joined in an open spacebetween the three spaced segmented vertical concrete columns, and aconcrete platform joined to upper ends of the vertical concrete columns.8. The foundation of claim 7, wherein the base has a bottom diameter anda top diameter and a sloped side surface, the bottom diameter greaterthan the top diameter.
 9. The foundation of claim 7, wherein the basetop diameter is approximately the same diameter of the body.
 10. Thefoundation of claim 7, wherein the base includes a central triangularaperture.
 11. The foundation of claim 7, wherein each beam frameincludes a plurality of structured beams selected from concrete beams ormetallic beams.
 12. The foundation of claim 7, wherein concrete segmentsforming each of the vertical concrete columns are semicircular and havesubstantially the same form and same dimensions.
 13. A pre-stressedmarine foundation, comprising: a base having a sloped side surface, atower placed on the base, the tower having a triangular cross-sectionformed by a plurality of spaced segmented pre-stressed vertical concretecolumns with a plurality of reinforcing beam frames joined in openspaces between the spaced segmented vertical concrete columns to realizea tower with annular structure and said triangular cross-section, and aplatform joined to upper ends of the vertical concrete columns.
 14. Thefoundation of claim 13, wherein the base includes a central triangularaperture.
 15. The foundation of claim 13, wherein each beam frameincludes a plurality of structured beams selected from concrete beams ormetallic beams.
 16. The foundation of claim 13, wherein concretesegments forming each of the vertical concrete columns are semicircularand have substantially the same form and same dimensions.
 17. Thefoundation of claim 13, further comprising a concrete layer added to thebase to increase weight of the base.